The present invention is applicable to any conventional sewing machine capable of producing a single line of stitches and relates to an apparatus cooperating with the sewing machine and together producing simultaneously parallel lines of stitches.
In the known sewing machine art, using a conventional sewing machine capable of producing only a single line of stitches, in order to produce parallel lines of stitches for instance for producing belt loops or the like, it was necessary first to sew a line of stitches at one side of the material and then to shift the part already sewn and in a second operation of the sewing machine to sew the second line of stitches parallel to the first line. As it can be understood, this known procedure involved a considerable waste of time which affected the working costs of the manufacture greatly.
The purpose of the present invention is to eliminate the aforesaid disadvantage by using a simple arrangement which permits simultaneous sewing of parallel lines of stitches. Moreover, the present invention is very easy to use, and above all permits rapid sewing of the material because no tedious guiding of the material is necessary to maintain perfect parallelism of the two stitched seams. This object of the invention is obtained by coupling the present apparatus with a conventional sewing machine provided with a single needle.
In the following specification this invention is disclosed as applied to an apparatus fitted up on a conventional lock stitch sewing machine, it being understood that this invention may be similarly applied to any other known type of single needle sewing machines.
The device of this invention is characterized essentially by an upper supporting frame including a vertically reciprocating needle carrying bar, as well as a lower work supporting structure including a rotating hook; the needle carrying bar and hook being set in motion through secondary shafts controlled by suitable kinematic transmission gears which are connected to a main driving shaft of the sewing machine, the secondary shafts being mounted on the sewing machine itself. The sewing operation carried out by the ancillary apparatus thus obtained being coordinated to the sewing operation of the main sewing machine also by means of reduction gears; these reduction gears being interposed through toothed belts or similar joint means both between the needle carrying bar and its corresponding upper rotating shaft, and between the loop taker and its corresponding lower shaft.